Dynamo-electric machine



0. E. WILSON. DYNAMO ELECTRIC MACHINE.

APPL'ICATION FILED MAR. 9. 1917.

1,389,1 10. Patented Aug. 30, 1921.

4SHEETSSHEET 1.

WITNESSES: INVENTOR 9nd 9% l/M Char/e5 E 147750 BY 3 z Mum AITTORNEY C. E. WILSON.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED MAR. 9,19l7- I 1 ,389,1 10. Patented Aug- 30, 1921.

4 sHEETs-sHEE'T 2.

3 a a s a i 1 WliNESSES: l INVENTO? g/Bw K/mr/es VI //50/7 ATTORNEY c. E. WILSON. f D YNAMO ELECTRIC MACHINE. APPLICATION FILED MAR. 9, WI].

1,389,110. Patented Aug. 30, 1921 '4 SHEETS-SHEET 4.

Work/kg Curran?- INVENTOR Char/es E, M7500 WITNESSES 7 ATTORNEY CHARLES E; WILSON, or WILKINSBURG, PENNSYLVANIA; ASSIGNOR T0 wnsrme- HOUSE ELECTRIC AND MANUFACTURING COMPANY,

SYLVAN IA. 1 i

a CORPQRATIQN or PENN- DYNAMO-ELECTRIC MACHINE.

Specification of Letters lateiit. Patented A g;- 39, 1921' Application filed March 9, 1917. Serial No. 153,538.

T 0 all whom it may concern: 7

Be it known that I, CHARLES E. WILSON, a citizen of the United States, and a resident of VVilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Dynamodtlectric Machines, of which the following is a specification.

My invention relates to dynamo-electric machines and especially of the regenerative operation of electric-railway vehicle 1110-,

tors of the direct-current, series-woundtype, and the like. I

The object of my invention is to provide a machine of the above-indicated character which shall be so designed andshall embody such features as to adapt it to become a stable series generator without requiring the customary additional excitation from an auxiliary source.

My invention may best be understood by reference to the accompanying drawing, wherein Figure 1 is a view, in front eleva-' tion, of ,a portion of the stator core ofa dynamo-electric machine constructed in accordance with my invention and showing the approximate relative proportions of the various stator teeth; Fig. 2 is a diagrammatic view, in development, of the stator, showing the location, in the core slots, of the several field windings; Fig. 3 to Fig. 5, inclusive, are diagrammatic views showing graphically the relations of certain fluxes in various parts of the machine, under predetermmed operating conditlons Flg.

6 is a curve chart indicating theregenerative operating characteristics of my machine; and F 7 is'a diagrammatic view representing the connection between the fields and the armature.

Referring to the drawing, the bi-polar machine shown comprises a rotor 1 and a stator 2. The rotor windings (not shown) may be of the usual direct-current type and are properly connected to acommutator 3 uponwhich a plurality of working-circuit brushes .4 and of short-circuited brushes 5 been a The WOIklIlg or supply-circuit brushes 4 are located in the usual commutating zones,

while the short circuited brushes 5 are positioned substantially at an angle of ninety electrical degrees therefrom, fora purpose to beset forth. i i e The stator'2 is provided with a plurality traced as follows of recurring sets of slots 6 that are adapted for containing a series-connectec distributed winding comprising main exciting 0011s 7' (solid lines) and compensating coils 8 (dotted lines), both of the concentric type, and also with a plurality of relatively large notches 9 that arejseverally located intermediate the sets of slots 6. Thus, thenotches 9 occupy positions that correspond to the centralportions of'the main polar faces in a dynamo-electric machine embodying salient polar projections. I have made the teeth 11 that correspond to the pole tips in a machine embodying polar RIOJGOtlOIlS, of relatively small cross-sectional area so that saturation will occur therein upon a relatively slight increase over normal flux.

Thus, beginning with any notch 9 and proceeding. in either direction, the "order of teeth s as follows: a relatively large body-' portion or main tooth 12, three of the poletip teeth 11, a commutating-pole tooth 13 of intermediate size, three more of the relatively small teeth 11, a large main tooth 12, another polar notch 9, etc.

ing to main polar projections are shown in thevertical axis and produce a flux inducing anelectromotove force by rotation at the main brushes 4, which are located opposite the commutating pole teeth 13. i

The short-circuiting brushes 5 are located on the center-lines of the notches 9 to aid the commutation of the coils -short-circuited. by those brushes, in accordance with prior practice. g r The coils '7 and 8 are preferably of the ordinary diamond type and are seriesconnectedin groups according to Fig. 2. A plurality offieldwinding taps 14: may be provided, if desired, for regulating purposesduring the regenerativeperiod. V

The machine circuit may, therefore, be from one machine tcr minal 20, through one'of the brushes 1-, the

armature windings not shown) the other brush 4, a main exciting coil 7 lIl'COIlIilJGP '80 In other words, the portions of'the stator correspond clockwise direction, conductor 21, a-se-cond c011 7.1nclockw1se direction, conductor 22,

clockwise direction, and thence tothe other machine terminal 24.

Although, for the sake of Simplicity and clearness, a machine correspondnig to the bi-polar type is illustrated, it Will be appreciated that my invention is not so restricted in its application.

It will be understood by those skilled in the art that armature reaction, which varies in proportion to the current, sets up a magnetic flux that tends to strengthen the exciting field in one tip, and weaken the field in the other tip, of each polar projection, as graphically set forth in Fig. 3.

By means of the above-described peculiar relations and arrangements of stator teeth and windings, the amount of compensation for armature reaction in the machine, that is, the efile-ctive ampere-turns and corresponding active unidirectional compensation flux, varies materially across each portion of the stator interior periphery that corresponds to a main polar face, as clearly shown in Fig. 3. In the main teeth 12 adjacent to each main polar notch 9, the machine is under-compensated, but the compensating effect, starting from a zero value at the outer edge of a main tooth 12, gradually increases under the relatively small pole tip teeth 11, and, under the commutating-pole tooth 13, a suitable positive or commutating flux is produced, as in the usual types of commutating-pole machines.

Referring to Fig. 3 the curve A represents the armature-reaction flux, being represented as a maximum over the tooth 13 and as tapering off to zero at the center lines of the exciting poles. The compensating-field flux is plotted in a line C on the other side of the axis from the curve A because of the fact that the compensating fiuX is in opposition to the armature reaction; For convenience in comparison, the curve A. has been plotted on the same side of the axis as the curve C and similar to the curve A. It will be noted that, by reason of the smaller baseline span or compensatingfield-\vinding pitch, curve A intersects the curve of compensating-field flux C twice between the.

auxiliary brushes 5, thereby producing an inner area X corresponding to the over-compensated portion of the stator interior face, that is, the commutating-pole tooth 18 and the adjacent parts on each side thereof, and two outer areas Y corresponding to the under-compensated portions, namely, the central parts of each main polar face.-

As illustrated in a simplified manner in Fig. 4, the design of parts is such that, under light-load or low-current values, the area X exceeds the combined areas Y; but, as the load increases, saturation rapidly occurs in the relatively small teeth 11 to cause no material increase in the areas X, while the areas Y increased by reason of the relative sizes and saturation conditions of the corresponding parts of the stator core. Thus, under relatively heavy-current conditions, as in regeneration, the areas Y exceed the area X, as indicated in Fig. 5, which condition is accompanied by a reversal of polarity of the auxiliary or short-circuited brushes 5.

The reversal of the polarity of the brushes 5 is caused by the fact that the eleetromotive force induced in the windings short circuited thereby is caused by a field which is the resultant of the armature-reaction flux and the fiux induced by the compensating winding 8. Under light load conditions the compensating fiux predominates and thecurrent in the short circuited coils produces a flux which aids the main field flux. Under heavy load conditions the armature-reaction flux predominates and the current in the short circuited coils is reversed, producing a field in opposition to the main field.

Thus, the combined or total compensating effect is positive with respect to, or aids the main exciting field flux under, light-current conditions, but is negative with respect to, or opposes, such flux, under relatively heavy current conditions in such manner as to cause the above-mentioned reversal of polarity of the short-circuited brushes. in other words, under light-load conditions, the machine is, on the average, over-compensated, but, under heavy-load conditions, is, on the average, under-compensated.

Stated still differently, under relatively heavy-load regenerative conditions, the polarity of the short-circuited brushes 5 is reversed, and the field-flux set up by the commutated coils tends to deniagnetize the main exciting field and, in consequence, at that time cause the machine to have a relatively rapidly drooping voltage-current characteristic, that is, the voltage decreases rapidly as the current increases. It is during the time that the machine is running under the relatively stable condition represented by the drooping portion of the characteristic that I propose to employ the motor as a gem era-tor for pumping back energy into the supply circuit. The characteristic in question is re n'esented by the curve of Fig. (3.

To increase the range of stable operation of the machine and thus obtain a greater return of energy to the supply-circuit, the main or exciting coils 7 may be divided into two equal parts, which, under initial or highspeed regenerative conditions, are connectm'l in series relation, Whereas, during the subsequent or low-speed portion of the regeilerative period, the winding halves are connected in parallel relation. The resultant field fluxes, under such main-field-winding conditions, are shown by the dotted lines S and 1, respectively, in Fig.3. The main-field or exciting ampere-turns are represented by the curve M. j

I do not Wish to be restricted to the specific structural details or arrangement of parts herein set forth, as various modifications thereof 'may be made without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed. as are indicated in the appended claims. I

I claim as my invention:

1. A direct-current dynamo-electric machine comprising a stator provided with main and compensating field pole pieces each provided with windings, an armature provided with windings certain of which are substantially short-circuited by means of current-collecting devices and certain others of which are connected externally by similar means, said short-circuited windings being adapted to produce a flux aiding said main field flux under light-load conditions and opposing said main field flux under heavy-load conditions.

2. A direct-current dynamo-electric machine embodying a rotatable member, a set of current-collecting devices associated therewith and adapted for external electrical connection, another set of currentcollecting devices associated with said rotatable member and inter-connected through a relatively low resistance, a magnetizable member having alternate projections and slots, and a plurality of conductors disposed in said slots and adapted, under predetermined conditions, to create a certain magnetic flux in said magnetizable member, certain of said projectionsbeing of such crosssectional area that saturation occurs first therein upon a predetermined increase in said flux, said rotatable member being disposed within the magnetic field of said magnetizable member.

3. In a direct-current dynamo-electric machine, the combination with a rotatable member provided with a plurality of conductors, of a set of current collecting devices adapted for connecting said conductors to an external electrical circuit, a second set of current-collecting devices interconnected through a relatively low resistance, a mag-' netizable member having alternate projections and slots, and a plurality of conductors disposed in a portion of said slots and normally adapted to create a certain magnetic flux in said magnetizable member, certain symmetrically recurring sets of said projections severally being of such cross-sec tional areas that saturation occurs therein upon a relatively slight increase in saidfiux, said rotatable member being adapted to rotate within the magnetic field of said magnetizable member. 7

9%. In a direct-current dynamo-electric machine,'the combination with a rotatable member provided'with a plurality of conductors, of a set of current-collecting devices adapted to connect said conductors to an external electrical clrcult, a second set of current-collecting devlces' disposed substansuch cross-sectional areas that saturation occurs therein upon a relatively slight increase in said flux whereby polarity of the several current-collecting devices in said second set s reversed.

5. A direct-current dynamo-electric mach1ne embodying a rotatable member havng a set of current-collecting devices associated therewith and adapted for external electrical connection, another set of currentcollecting devices associated with said rotatable member and inter-connected through a relatively low resistance, a magnetizable member having alternate projections and slots, a plurality of conductors disposed in said slots and adapted, under predetermined conditions, to create a certain magnetic flux in said magnetizable member, and means for varying the magnetic effect of said Yconductors, certain of said projections being of such cross-sectional area that saturation oc curs first therein upon a predetermined increase in said flux, said rotatable member being disposed within the magnetic field of said magnetizable member.

6. In a dirct-current dynamo-electric machine, the combination with a rotatable member provided with a plurallty of conductors, of a set of current-collecting devices .adapted to connect said conductors to an external electrical circuit, a second set of current-collecting devices disposed substantially 9O electrical degrees from the first set llO and inter-connected through a relatively low-resistance, a magnetizable member having alternate projections and slots, a plurality of conductors disposed in a portion of said slots and normally adapted to change a certain magnetic flux in said magnetizable member to effect areversal of polarity of th several curi'entcollecting devices in said second set, and means for varying the mag- I netic effect oisaid conductors, certain symmetrically recurring sets of said projections severally being of such cross-sectional areas that saturation occurs thereinupon a rela-' tively slight increase in said flux whereby the polarityoit the several current-collecting devices in said second set is reversed.

In testimony whereof, I have hereunto sub sjcribed my name this 28th dayof Feb. 191 I eHAnLEs n WILSON. 

